3DS Forum

Positives
-Takes about an hour and a half to fully train a monster.
-Is the most effective way to gain EVs.
-Gives you large punching bags if you're quick enough.

Negatives
-Forces you to train and master each stat difficulty level before giving you the higher stat increasing levels.
-Doesn't give you a number in the EV tally, only a green hue inside a graph. However, it does tell you when you can't raise the stat anymore and I think it maxes each stat out at 252.